Centrifugally cast pipe fittings

ABSTRACT

An apparatus for centrifugally casting wherein a plurality of molds surround a resin tank on a centrifuge table. Feed lines communicate between each mold and the lower portion of the tank. Vent lines communicate between each mold and the upper part of the tank.

O Unlted States Patent 1151 3,642,399 Barainsky et al. 1 Feb. 15, 1972[54] CENTRIFUGALLY CAST PIPE [56] References Cited FITTINGS UNITEDSTATES PATENTS [72] Inventors: Rudolf F. Barainsky, Bardenberg-Pley; 1293 535 2/l9l9 y .264/311 x Richard B'irglsch-sladbach 2,442,718 6/1948Woock.... ..l8/26 RR ux r Llblar; Alfred 2,885,733 5/1959 Chupa..264/302 Eschwellefa Germany 2,993,235 7/1961 Brown et a] ..264/31 1 x[73] Ass1gnee: I;De;a|:\t)sche Fibercast GmbH, Aachen, Ger- FOREIGNPATENTS OR APPLICATIONS [22] Filed Oct 9 1969 1,060,959 11/1953 France..264/3ll [21] Appl. No.: 864,999 Primary ExaminerRobert L. Spicer, Jr.

Att0mey.l. Vincent Martin, Joe E. Edwards and M. H. Gay

57 ABSTRACT [52] US. Cl ..425/117, 264/31 1,425/169, I

425/217 An apparatus for centnfugally castmg wherem a plurahty of 511111. c1. ..B29c 5/04 molds Surround a resin tank a centrifuge tableFeed lines [58] Field of Search ..264/302, 297, 257, 310, 31 1;communicate between each "101d and the P of the 25/9, 26, 29; 18/26 RR,26 R tank. Vent lines communicate between each mold and the upper partof the tank.

6 Claims, 2 Drawing Figures CENTRIFUGALLY CAST PIPE FITTINGS Theinvention concerns an arrangement for the manufacture of preferablyglass-fiber reinforced castings of casting resin, for instance, epoxyresin.

To obtain castings of high strength and smooth surface, it is necessaryto condense the resin in the mold. For this reason the known open molds,in which layers of fibers and resin are placed alternatingly, must bediscounted. But with the conventional molds which can be closed and inwhich the filling operation is carried out under pressure it is also notpossible to achieve a strength of the castings which would be comparablewith that of castings or rotational symmetry made by the centrifugalcasting process.

It has therefore already been proposed to move closed molds along acircular path and to connect the lower part of each mold, via pipes, toa tank which is filled with resin and which is arranged between the axisof rotation of the path and the molds and to provide organs in the upperpart of each mold for the venting of air from the closed mold (GermanPat. No. 1,225,372).

Although a moderate degree of densification of the resin can be achievedwith this arrangement in the molds moving in a circular orbit, onlyforms of a certain shape, which, for instance, have no undercuts, can befilled with the resin, without voids as for instance, a part which iscloser to the axis of rotation of the molds than the point of the resinfeed or air venting, respectively, can eventually no longer be ventedand remains void of resin. But also the air bubbles which invariablyappear in the molding material have therefore no opportunity to escapefrom the mold.

The invention addresses itself to the task to create a simplifiedarrangement for the manufacture of castings which produces a completelycondensed structure of the casting, free of voids, in a short time andindependently ofthe shape of the molds.

Starting out with an arrangement for the manufacture of preferablyglass-fiber reinforced castings of casting resin, for instance, epoxyresin which during the molding process is subjected to a centrifugalforce, wherein it flows into the cavities, containing glass-fiberfabric, of parted molds which move along a circular path, the task issolved according to the invention by that the molds are arranged along acircle about the axis of rotation in such a manner that each mold islocated closest to the fulcrum only with a narrowly limited part of itscavity and is connected at that point with two pipe lines, one of whichfeeds the resin from a centrally arranged tank into the mold, while theother serves for the venting ofthe mold.

in contrast to the known arrangement the design according to theinvention dispenses with multiple tanks, which due to the relativelyshort setting time of the resins require suitable attention after eachmolding operation, and instead uses only one, centrally arranged tankfor all molds.

lt is true that in the proposal described above the possibility isconsidered to provide only one tank for all molds. As the tank, however,should be given a place between the axis of rotation and the mold, thetank would have to have excessively long; winding pipe lines which,aside from the cost, impede an accelerated transport of the resin andencourage clogging of the lines and uneven distribution to theindividual molds.

In addition to the simplified design of the arrangement according to theinvention, there is the considerably more significant advantage thateven more complicated shapes of the castings do not prevent a structurefree of voids, as due to the effective centrifugal force the part of thecavity closes to the fulcrum is vented in any event up to the lastmoment and remains accessible to the resin.

Especially intensive densification can be obtained through a furtherdevelopment of the arrangement according to the invention by mountingthe molds on a rotary table which drives via a planetary gear the tankat the center of the table at the same angular speed at alternatinglyincreasing and decreasing distance from the individual molds.

In this arrangement the invention exploits the pulsating increase anddecrease of the centrifugal force action due to the constantly changingradius and therewith achieves a densification unsurpassed by the knowncentrifugal casting methods. Additionally, the invention achieves theeffect with this arrangement that because of the constant change of theradius the resin in the tank is subjected to thorough mixing and thatthe feed lines remain in motion, which counteracts the danger ofclogging.

But even with a fixed arrangement of the tank at the center of therotary table, the arrangement according to the invention achievescastings with strength known from the conventional centrifugal castingmethod. With this arrangement can be produced, for instance, pipe elbowswhich find application in pipe line systems with pipes made by thecentrifugal casting method and can stand the same stresses withoutdamage, as extensive tests have confirmed.

In order to perform the molding operation in a short time and not tohave to continue driving the rotary table until the castings solidify,the invention proposes to arrange the tank adjustable in height, butwith the lowest point of its interior at the same level or higher thanthe highest point of the cavity of the molds.

Through this arrangement the not yet solidified resin is prevented fromreturning to the tank completely or partially as soon as it is no longersubjected to the centrifugal force.

How little obvious the simple solution of this problem according to theinvention is, is demonstrated by an elaborate proposal of recent timewhich provides to close the molds after the filling operation with aresin which hardens faster than the filled-in resin (German Pat. No. 1,]13,009).

The arrangement of the tank in accordance with the invention hasfurthermore the effect that due to the level difference resin flowstoward the molds already before the rotation of the centrifuge tablestarts. Thereby the resin which has already fiowed to the molds is actedupon, when the centrifuge table starts to rotate, by a centrifugal forceincreased in accordance with the increased radius, which draws theremainder of the resin from the tank in a continuous flow, so that theresin still .in the tank is subjected, in addition to the lessercentrifugal force due to the smaller radius, to an intensive suctionforce. The tank can therefore be given, without consideration of thecentrifugal force, a relatively small diameter without the resultingsmall centrifugal force in the interior of the tank have a detrimentaleffect on the material flow, as the suction force does not permit thestream of resin to tear off.

The invention proposes furthermore that the venting line is led fromeach mold upward in the direction of the axis of rotation and has acapacity which is equal or greater than the capacity of the feed line.

With this design the invention assures the quantity of resin which issubject to the centrifugal force and which may possibly be too largecannot exit toward the end of the molding process through these ventinglines as the venting line can take up at least the same amount ofcasting resin as the feed line and centrifugal forces of the samedirection are effective in both lines.

Finally the invention also proposes that an organ is arranged in theventing line which indicates the end of the filling process so that theoperating personnel can terminate the rotation of the molds after thecompletion of the molding process with an accurately determinable delay.For the purpose of automatizing, the organ in the venting line can,however, also be connected with a timing relay which terminates themolding process automatically, according to the invention.

An example of implementation of the arrangement according to theinvention for the manufacture of pipe elbows is shown schematically inthe drawing and is described in greater detail in the following:

H0. 1 shows the arrangement in a vertical cross section and;

PK]. 2, in top view.

On a horizontally arranged centrifuge table 1 which is supported by ashaft 3 driven via a pinion 2 a tank 6 containing resin 5 is attached ona centrically arranged console 4.

In the sidewall of the tank 6 are connected, directly above the bottom,feed lines 7 which are in connection with the cavities 8 of the molds 9for the manufacture of pipe elbows which are arranged on the centrifugetable 1 along a circular path.

The molds 9 are arranged on the centrifuge table 1 in such a manner thateach cavity 8 is closest to the axis of rotation of the centrifuge table1 with a tangent of the outer arc.

At the tangent is connected to the cavity 8 of each mold 9, next to themouth of the feed line 7, a venting line 10 which is brought into theupper part of the tank 6 so far that its end piece 11 goes through theparaboloid of the liquid.

A bell l3 equipped with heat radiators 12 and enclosing a ring-shapedspace is suspended in floating condition by the chains 14 which can moveup and down, and serves to heat the molds 9 arranged on the centrifugetable 1, the tank remaining unheated.

The manner of operation of the arrangement is as follows:

After the cores wound with glass fiber have been placed in the partedmolds 9, the lines 7 and 10 are introduced into the recesses provided inthe parting plane of the molds 9 and the upper parts of the molds areput in place and firmly connectedwith the lower partsv Hereupon aquantity of resin corresponding to the cavities 8 is filled into thetank 6 and the heating bell 13 is brought into the position shown inFIG. 1.

Because of the rotation of the centrifuge table which has now startedthere acts on the resin which has partially flowed to the molds due tothe difference in level, a centrifugal force which draws the remainingresin from the tank 6 and subjects it also to an increasing centrifugalforce. While the glass fibers in the cavities are thereby beingimpregnated the casting are built up from the outside toward the insideto the axis of rotation of the centrifuge table 1 without voids and,after a short spinning time, exhibit a very high strength in thehardened condition.

What is claimed is:

l. Arrangement for the manufacture of preferably glassfiber reinforcedcastings of casting resin, for instance,

epoxy resin which is subjected to a centrifugal force during the moldingprocess,

wherein it flows via pipes to cavities which contain the glassfiberfabric, of parted molds (9) moving along a circular path, characterizedby that the molds (9) are arranged about an axis of rotation on a circlein such a manner that each mold (9) is closest to the center of rotationonly with a narrowly limited part of its cavity (8) and is'connected atthis pint to pipe lines (7; 10),

of which always one line (7) feeds the resin (5) from a centrallyarranged tank (6) into the mold (9),

while the other line (10) serves for the venting and overflow of themold (9) and returns to the fili tank.

2. Arrangement according to claim 1, characterized by that the molds (9)are mounted on a rotary table (1) which drives the tank (6) at thecenter via a planetary gear at the same angular speed at altematinglyincreasing and decreasing distance from the individual molds (9).

3. Arrangement according to claim 1,

characterized in that the tank (6) is arranged adjustable in height, butwith the lowest point of its interior space at the same level or higherthan the highest point of the cavity (8) of the molds (9).

4. Arrangement according to claim 1,

characterized in that the venting line (10) is brought upwards in thedirection of the axis of rotation and has a capacity which is equal orgreater than the capacity of the feed line (7).

5. Arrangement according to claim 1,

characterized in that in the venting line (10) provides an organindicating the completion of the filling operation. 6. Arrangementaccording to claim 2, characterized in that the tank (6) is arrangedadjustable in height, but with the lowest point of its interior space atthe same level or higher than the highest point of the cavity (8) of themolds (9),

that the venting line (10) is brought upward in a direction of the axisof rotation and has a capacity which is equal or greater than thecapacity of the feed line (7) and that the venting line (10) provides anorgan indicating the completion of the filling operation.

1. Arrangement for the manufacture of preferably glass-fiber reinforcedcastings of casting resin, for instance, epoxy resin which is subjectedto a centrifugal force during the molding process, wherein it flows viapipes to cavities which contain the glassfiber fabric, of parted molds(9) moving along a circular path, characterized by that the molds (9)are arranged about an axis of rotation on a circle in such a manner thateach mold (9) is closest to the center of rotation only with a narrowlylimited part of its cavity (8) and is connected at this pint to pipelInes (7; 10), of which always one line (7) feeds the resin (5) from acentrally arranged tank (6) into the mold (9), while the other line (10)serves for the venting and overflow of the mold (9) and returns to thefill tank.
 2. Arrangement according to claim 1, characterized by thatthe molds (9) are mounted on a rotary table (1) which drives the tank(6) at the center via a planetary gear at the same angular speed atalternatingly increasing and decreasing distance from the individualmolds (9).
 3. Arrangement according to claim 1, characterized in thatthe tank (6) is arranged adjustable in height, but with the lowest pointof its interior space at the same level or higher than the highest pointof the cavity (8) of the molds (9).
 4. Arrangement according to claim 1,characterized in that the venting line (10) is brought upwards in thedirection of the axis of rotation and has a capacity which is equal orgreater than the capacity of the feed line (7).
 5. Arrangement accordingto claim 1, characterized in that in the venting line (10) provides anorgan indicating the completion of the filling operation.
 6. Arrangementaccording to claim 2, characterized in that the tank (6) is arrangedadjustable in height, but with the lowest point of its interior space atthe same level or higher than the highest point of the cavity (8) of themolds (9), that the venting line (10) is brought upward in a directionof the axis of rotation and has a capacity which is equal or greaterthan the capacity of the feed line (7) and that the venting line (10)provides an organ indicating the completion of the filling operation.